1. Field of the Invention
This invention relates to package wrapping machines and especially to such machines adapted for use in wrapping lumber which has previously been banded together
2. Description of the Prior Art
The industry standard for lumber packages is two feet high by four feet wide. These packages may vary in length and may be, for example, 8 feet long, 10 feet long, 20 feet long, 28 feet long, or longer. Each package contains a plurality of individual lumber products which may themselves vary in length, but are held together in a unitary bundle by straps which are attached around the periphery of the package in a previous operation. In order to protect the lumber package from the elements, it is necessary to apply a layer of plastic film or paper over the package, leaving the bottom open for air circulation in order to inhibit lumber mildew or fungus growth.
The prior art consists mainly of a manual operation wherein sheeting is applied to the top and four upstanding sides of the lumber package. The industry practice is to use staples which actually enter the products being packaged for holding the wrapping material to the product.
A number of automated package wrapping machines are also known in the prior art. Included among these are:
U.S. Pat. Nos.
545,397--Aug. 27, 1895 PA2 2,215,544--Sept. 24, 1940 PA2 2,671,998--Mar. 16, 1954 PA2 2,737,002--Mar. 6, 1956 PA2 3,153,300--Oct. 20, 1964 PA2 3,307,326--Mar. 7, 1967 PA2 3,429,098--Feb. 25, 1969 PA2 3,486,294--Dec. 30, 1969 PA2 3,685,253--Aug. 22, 1972 PA2 3,750,361--Aug. 7, 1973 PA2 3,832,822--Sep. 3, 1974 PA2 3,986,319--Oct. 19, 1976 PA2 4,077,179--Mar. 7, 1978.
These automated prior art systems are relatively complex and are generally adapted for wrapping articles having fixed predetermined dimensions. None of these prior art devices has been found to be readily adaptable for use in packaging lumber products having various lengths.